This invention relates to a portable image analysis system whereby documents and even raw paper can be inspected in situ.
Raw paper is inspected and printers are tested, after printing a sample document, by stationary, fairly large image quality measurement systems which typically include a vibration isolation table, an X-Y translation stage, multiple cameras and illumination sources, and a computer operating a program like ImageXpert(trademark) available from KDY, Inc., Nashua, N.H.
There is often a need, however, to spot check or inspect raw paper as it is manufactured and also a need to spot check or inspect one or more printers as they are in the process of printing sample documents.
Since traditional stationary image quality measurement systems are quite expensive and bulky, they are typically positioned in the factory in a specific test area or bay and thus they cannot easily be brought out onto the factory floor. Therefore, quality assurance personnel must transport samples to the test area, a process which increases the likelihood that samples will be damaged or lost in transit. Moreover, there is a time delay between sample collection and analysis which can adversely affect the inspection processes.
Currently, there is no known hand held camera based system for inspecting raw paper as it exits a particular paper making machine or for inspecting sample or test documents as they are printed by a new printer.
It is therefore an object of this invention to provide a portable image analysis system.
It is a further object of this invention to provide such a portable image analysis system which can be easily brought or carried onto the factory floor and used in situ to inspect raw paper, documents, and other surfaces.
It is a further object of this invention to provide such a portable imaging analysis system which is fairly inexpensive, reliable, and simple in design and construction.
This invention results from the realization that the features of documents, blank paper, and other surfaces can be spot checked and inspected in situ by (a) the combination of a lap top computer running an image quality analysis program coupled to a head assembly about the size of a computer mouse which includes a CCD camera, an imaging window, a number of LED light sources aimed at the window, and a diametrically opposed viewing window which allows the operator to correctly and precisely position the head assembly over the surface, (b) by the addition of a switching circuit for strobing the LED light sources at different frequencies depending on the reflectivity of the surface to eliminate the need for a mechanical aperture, and (c) by the addition of an integral calibration target which is disposed on the bottom of the head assembly and which can be slid out over the imaging window to calibrate the system.
This invention features a portable image analysis system including a hand held head assembly and a computer coupled to the head assembly. The head assembly has a housing, an imaging window in the bottom of the housing, at least one light source such as an LED in the housing directed at the imaging window, and an imaging device such as a CCD in the housing optically coupled to the imaging window. The computer typically includes an imaging quality analysis program and a monitor for displaying images in the imaging window of the housing captured by the imaging device of the hand held head assembly for performing in situ image quality measurements.
The housing preferably also includes a viewing window in the top thereof diametrically opposed from the imaging window, the viewing window optically coupled to the imaging window to allow an operator to correctly position the imaging window of the hand held head assembly over an area of interest. There is typically a beam splitter in the optical path between the imaging window and the viewing window, a lens responsive to the beam splitter, a mirror positioned to direct light from the lens onto the CCD, and a fixed iris or aperture device positioned between the lens and the mirror.
There are typically a plurality (e.g., four) LED light sources all directed at an angle with respect to the imaging window. Further included are means for strobing the light sources and means for adjusting the strobing frequency of the light sources to regulate the amount of light directed through the imaging window. Also included is a calibration target and means, such as a sleeve in the bottom of the housing proximate the imaging window, for removably positioning the calibration target under the imaging window for calibrating the system.
This invention also features a hand held assembly for a portable imaging system, the hand held assembly comprising a housing, an imaging window in the bottom of the housing, at least one light source in the housing directed at the imaging window, an imaging device in the housing for capturing an image of an object (e.g., a sample document) placed under the imaging window, and a switching circuit in the housing for adjusting strobing frequency of the at least one light source, the switching circuit including a processor responsive to a varying resistance switch input.